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The disk is a popular tillage tool in some regions, such as the prairies of western Canada, because it has advantages relative to the mouldboard plow in these regions. The disk was developed about 100 yr ago (Ingersoll 1926), and until recently the only disk shape was spherical (Figure 1). A variation of the spherical disk is one with two radii usually referred to as a double concavity disk. Ingersoll (1926) records that the double concavity disk was developed as a result of a manufacturing error. A recent innovation is the conical disk with the basic shape of a right circular cone. Originally each disk was mounted on the implement frame independent of the other disks. Because of costs, the common disk implement today is one with the disks mounted in gangs, such as the tandem disk harrow. Another implement which uses disks mounted in gangs is one that is unique to western Canada, the one-way disk harrow. A general force equation proposed by Gill and Vanden Berg (1967) for tillage tools states that the soil reacting forces are a function of the tool shape and orientation. With the recent introduction of the conical disk it is an appropriate time to determine the reacting forces for this disk and compare the results with the reacting forces for the spherical disks. In pursuing these objectives, some equations with regard to the geometry of the disk and the location of the wrench or screw axis were derived.
soil reacting forces from laboratory measurements with disks
Harrison, H.P. and T. Thivavarnvongs 1976. SOIL REACTING FORCES FROM LABORATORY MEASUREMENTS WITH DISKS. Canadian Agricultural Engineering 18(1):49-52.
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